With diplomats expected to meet next week to discuss Iran's nuclear program, tensions over Crimea are raising questions about the path forward.
"I think we all hope that the incredibly difficult situation in Ukraine will not create issues for this negotiation," a senior administration official said Friday.
Diplomats from the United States, the United Kingdom, France, Germany, Russia, China, and Iran are expected to meet in Vienna. Catherine Ashton, the European Union's foreign policy chief, wll also be involved in the talks, which will focus on reaching a final agreement.
"We hope that whatever happens in the days ahead, whatever actions that we in the international community take depending on the decisions and choices that Russia makes, that any actions Russia subsequently takes will not put these negotiations at risk," the official said.
Negotiators from the seven countries reached an interim agreement in November. Under that agreement, countries have until late July to reach a long-term deal, which the official compared to completing a Rubik's cube because of the separate, yet interconnected, issues.
Whether or not that effort will be complicated by the current low point between U.S. and Russia remains to be seen.
Tensions between the two countries have been on the rise since Russian troops went into Crimea, which sits along the Ukrainian-Russian border. Those tensions could peak on Sunday when Crimea is scheduled to have a vote on if it should secede from Ukraine.
Russian President Vladimir Putin has backed such a move, while U.S. and western officials have unanimously dismissed it and warned that it won't be internationally recognized.
Secretary of State John Kerry and Russian Minister Sergey Lavrov met in London on Friday in the diplomatic equivalent of a Hail Mary pass aimed at trying to deescalate the situation.
Kerry — while calling the talks "candid," "constructive," and "frank" — said that Lavrov was clear "that President Putin is not prepared to make any decision regarding Ukraine until after the referendum."
But Kerry noted that if the referendum takes place "there will be some sanctions. There'll be some response, put it that way."
His comments follow those to members of Congress earlier this week, in which he warned that the Ukraine crisis could "get ugly fast if the wrong choices are made."
"Russia has challenges of its own, and I'm not sure they need to have the kind of economic constraints that may be following, depending on the decisions they make," he said while testifying before a House Appropriations subcommittee Wednesday.